1. Field of the Invention
This invention relates to deconfliction of guided airborne weapons fired in a salvo against a group of targets. The invention is applicable to weapons provided with either a single mode seeker that includes an imaging sensor such as an active RF/MMW or passive EO (e.g. IR) or a multimode seeker that includes one or more imaging sensors and a non-imaging semi-active laser (SAL) sensor.
2. Description of the Related Art
A guided missile maneuvers in response to guidance signals to impact a target. A class of guided missiles referred to as Lock On After Launch (LOAL) are provided an initial target cue (e.g. time-stamped position, velocity and uncertainties of both and possibly target discriminators), which may be updated with in-flight target updates (IFTUs). The missile propagates a cued track file for the target based on the initial target cue and any IFTUs. The track file estimates the position, velocity and uncertainty volume of the target. A target's uncertainty volume is that volume of space in which a target could reasonably be expected to be based on the initial cues and any IFTUs, changes in target motion since the last cue and uncertainty in the weapon's position.
Once the missile is within range, the seeker searches the uncertainty volume looking for target-like objects (TLOs) that have a signature of a possible target based on position, speed, brightness (IR), strength of return (RF) or other discriminators such as size or shape and correlates each TLO track file with the cued track file to find the best match. The seeker may include an imaging sensor such as a passive electro-optical (EO) sensor (e.g. an infrared (IR) sensor) or an active radio frequency (RF) or millimeter wave (MMW) sensor or some combination thereof to acquire and track the TLOs. The seeker may search the uncertainty volume by using a fixed wide field of view (FOV) sensor, maneuvering the missile, slewing the seeker via a gimbal or, in the case of RF or MMW sensors, by electronically scanning the FOV.
A multimode seeker also includes a semi-active laser (SAL) sensor that tracks laser energy provided by a laser designator (e.g. a ground or airborne designator) reflected off a target or nearby landmark (known as “offset designation”). The laser pulses are coded and must match the code keyed into the missile prior to launch.
If the target is not illuminated with a laser, the multimode seeker uses the imaging sensor to select the likeliest TLO and maneuver to impact. If the target is illuminated with a laser, the multimode seeker uses the SAL information to confirm or override the correlation match. If the laser is left on until impact (known as “SAL designation”), the missile seeker tracks the laser information all the way to impact ignoring the imaging sensor image and correlation. If the laser is only on a brief period (known as “SAL anoint”), the missile seeker finds the closest TLO to the cue and uses the imaging sensor(s) to track the TLO to impact.
If as illustrated in FIGS. 1a through 1c multiple LOAL guided missiles 10 are fired in a salvo to enter the same target space 12 and prosecute multiple targets 14 simultaneously, the likelihood that targeting conflicts or ambiguity will arise is quite high. As the missiles fly toward the target space, the uncertainty volume 16 associated with a target cue 18 grows increasing the possibility that the uncertainty volumes for different targets will overlap and cause a conflict or ambiguity. Each missile scans a search volume 20 that spans the uncertainty volume 16 for its target cue 18. Multiple missiles may track and commit to the same target leaving one or more targets safe. In fact, for closely spaced targets it is quite likely that all of the missiles may select the same target.
This problem may be solved by simultaneously illuminating each target with a different laser designator having a different laser code. Each missile is keyed with a different one of these codes. Each missile acknowledges only the SAL return for which it is keyed and tracks that designation to impact. Unfortunately, this solution is neither cost effective, practical or safe in a combat environment.
Instead the current solution is to provide a single laser designator and key all of the missiles to the same laser code. The missiles are fired sequentially. Each missile acquires and tracks the SAL designation to impact a target. The designator moves from one target to the next until all of the missiles have been fired to prosecute the set of targets. The approach resolves the targeting ambiguity but sacrifices the benefits of firing a salvo of missiles. The benefits of prosecuting the target space with a salvo include maintaining an element of surprise on the enemy and minimizing the exposure of both the laser designator and the missile launch platform(s).